The invention relates to a variable valve control arrangement for piston-type internal combustion engines having cylinders with a cylinder head including exhaust valves and intake valves whose opening period is adjustably controlled by two camshafts whose angular positions relative to each other are adjustable during operation of the engine.
Valve operating mechanisms for piston-type internal combustion engines are known in various arrangements. In practice, the intake valves and the exhaust valves are operated generally by a common camshaft, but it is also known to provide separate camshafts for operating the intake and exhaust valves. The valves are actuated directly by the cams of the respective camshaft or they are operated by the cams by way of intermediate rocker arms.
Also variable valve control arrangements are known, for example from DE 43 22 480 C2, particularly for the intake valves of piston-type internal combustion engines wherein the intake valves are controlled by two camshafts of which one has the function of opening the inlet valves and the other has the function of closing the intake valves, and the relative phase positions of the two camshafts can be changed by a controllable coupler drive disposed between the two camshafts depending on engine operating parameters. The cams of the two camshafts controlling the intake valves act on a common engagement member which is disposed on a valve operating rocker arm which is supported so as to move in a plane extending normal to the axes of the camshafts. The intake valves of the cylinder of the internal combustion engine are operated by the respective rocker arms.
DE 197 01 203.5 already discloses a variable valve control for a piston-type internal combustion engine with exhaust valves operated by a camshaft by way of rocker arms and with two additional camshafts of which one controls the intake valve opening functions and the other, the intake valve closing functions. This arrangement results in a relatively wide cylinder head and is relatively expensive as it requires a large number of parts.
It is the object of the present invention to provide a variable valve operating mechanism for piston-type internal combustion engines which requires less space and which is less expensive than the prior art arrangements.